Stent device delivery system with inwardly tapering stent bed

ABSTRACT

A stent device delivery system and method of making. The stent device delivery system includes a stent device, an outer sheath overlaying the stent device in a radially compact, delivery configuration of the stent device, and an inner catheter extending axially and radially within a lumen of the stent device. The inner catheter provides a stent bed upon which the stent device is located so that a radially inner surface of the stent device engages a radially outer surface of the stent bed. The stent bed may define an inwardly tapering profile, narrowing in radius from a distal portion of the stent device to a proximal portion of the stent device.

PRIORITY

This application claims the priority benefit of U.S. ProvisionalApplication No. 61/266,299, filed Dec. 3, 2009, and U.K. PatentApplication No. 0921238.2, filed Dec. 3, 2009, each of which isincorporated by reference in its entirety into this application.

FIELD OF THE INVENTION

The present invention relates to a stent device delivery systemcomprising a stent device and an outer sheath overlaying the stentdevice. The outer sheath is axially retractable relative to the stentdevice in order to deploy the stent device. The present invention alsorelates to a method of making the stent device delivery system.

BACKGROUND

Stent device delivery systems are known in the art. The purpose of sucha system is to deliver a stent device to a diseased vascular lumen. Thestent device provides a support structure against collapse of thediseased vascular lumen. There are at least two types of stent devicedelivery systems that are of relevance to the present invention.

A first type provides a rolling outer sheath for deploying a stentdevice. Such a “rolling” outer sheath system is disclosed, for example,in U.S. Pat. No. 6,544,278, which is incorporated by reference in itsentirety into this application. The outer sheath is made from a tubularsleeve that is folded back upon itself in order to define an innerlayer, an outer layer and a fold-over portion connecting the inner layerand the outer layer. The inner layer and the outer layer overlay thestent device in a delivery configuration of the stent device. The outerlayer is axially movable relative to the inner layer in a proximaldirection, which causes the fold-over portion to move axially from adistal end to a proximal end of the stent device in a rolling manner,thereby retracting the outer sheath from the stent device. The stentdevice, unconstrained by the outer sheath, is able to radially expandinto an operative configuration for supporting the diseased vascularlumen.

A second type of prior art delivery system provides an outer sheath thatslides, rather than rolls, over the stent device in retracting the outersheath from the stent device. Such a delivery system is disclosed in,for example WO 2006/133959, which is incorporated by reference in itsentirety into this application. In this “pullback” outer sheath system,a proximal end of the outer sheath is pulled upon in order to drag theouter sheath axially from the stent device.

In terms of deployment force, rolling outer sheath delivery systems areadvantageous in some circumstances as compared to pullback outer sheathdelivery systems. In pullback outer sheath delivery systems, frictionbetween the outer surface of the stent device and the inner surface ofthe outer sheath has to be overcome in order to move the outer sheathrelative to the stent device. The longer the stent device, the greaterthe friction that has to be overcome. This puts certain constraints onwhat materials can be used for the outer sheath because of strengthissues. Rollback outer sheath delivery systems are not as constrained byhigh frictional force considerations, but deployment force can still bea problem as, during rollback, the fold-over portion must generallyslide against a more proximal portion of the inner layer. However,two-layer rollback constructions can disadvantageously increase thecross-sectional profile of the stent relative to single-layer pullbackconstruction. In order to allow for a rolling outer sheath deliverysystem of comparable profile to a pullback system, the outer sheath ismade of thinner, and thus weaker, materials than an equivalent pullbackouter sheath delivery system. However, if the friction during rollbackexceeds the strength of the materials used, reliability of the rollingouter sheath stent delivery system may be jeopardized.

In both the pullback outer sheath delivery stent device delivery systemsand the rolling outer sheath stent device delivery systems, a pullmember is used to apply a pulling force to retract the outer sheath fromthe stent device. The pull member may extend from a handle portion to aposition just proximal of the stent device where it is attached to theouter sheath. One way to attach a pull member to an outer sheath isdisclosed in WO 2006/133959, which is referred to above. In thisdocument, outer and inner bands are arranged with the outer sheathcompressed between them. A pull wire or pull member is brazed to theinner band and runs all the way back to a handle portion of the stentdevice delivery system. A strong and reliable connection between thepull member and the outer sheath is essential for successful deploymentof the stent device by retracting the outer sheath. It is desirable toprovide an alternative manner of strongly attaching the pull member tothe outer sheath, while also retaining a low profile configuration.

Accordingly, in one embodiment, provided is a stent device deliverysystem that is reliable in terms of deployment of the stent device byretracting the outer sheath and is low profile for ease of delivery ofthe stent device to the diseased vascular lumen site. In one embodiment,provided is a method of making such a stent device delivery system.Other advantages of features of the present invention will becomeapparent to the skilled reader from the following description ofembodiments of the invention.

SUMMARY

In one aspect, the present invention provides a stent device deliverysystem comprising a stent device and an outer sheath overlaying thestent device in a radially compact delivery configuration of the stentdevice. The outer sheath is retractable relative to the stent device inorder to allow radial expansion of the stent device to a deployedconfiguration of the stent device. The outer sheath comprises a firstlayer of polymeric material (or plastic layer) and a reinforcement layerof polymeric material (or reinforcement plastic layer) that arelaminated together. In a preferred embodiment, the first layer and thereinforcement layer are glued together by a glue layer radially betweenthe first layer and the reinforcement layer.

The first aspect of the present invention allows the outer sheath to bemade of plastic layers, which allow the outer sheath to be maderelatively thin as compared to some prior art outer sheaths. Suitableplastic materials for the outer sheath, as many polymers, are generallyneckable under tension from a pull element which would cause the outersheath to reduce in diameter. This reduction in diameter may result inan increased radial compression on inner components of the systemresulting in an increased deployment force. This, if beyond a maximumallowable threshold for the sheath, could give rise to deploymentfailure. The reinforcement plastic layer of the first aspect of thepresent invention strengthens the first plastic layer, while thepreferred presence of the glue layer has been found to strongly inhibitnecking of the first plastic layer and the reinforcement plastic layer,as glues typically are not substantially ductile when set or cured. Thiscombination of layers has been surprisingly found to offer a thin outersheath that reliably deploys without undue increase in deployment force.

Preferably, the first layer, the reinforcement layer and, where present,the preferred glue layer overlay, and thus extend along, the stentdevice. Necking of the outer sheath in the region of the stent devicewould particularly present a barrier to successful retraction of theouter sheath from the stent device.

In another preferred embodiment, the outer sheath comprises a distalportion overlaying the stent device and a transition portion proximal ofthe stent device, wherein the transition portion tapers in a proximaldirection. Preferably, a portion of the outer sheath proximal of thetransition portion includes the first layer, the reinforcement layer andpreferably, the glue layer of the outer sheath. Preferably, the taperingportion includes the first layer, the preferred glue layer and thereinforcement layer. It has been found in practice that the outer sheathis particularly stressed at the transition portion and proximal to thetransition portion when being pulled for retraction from the stentdevice. Accordingly, provision of the reinforcement layer and thepreferred glue layer at at least one of these locations is particularlyadvantageous for the avoidance of failure.

The stent device delivery system preferably further comprises a pullmember attached to the outer sheath to be pulled upon in order toretract the outer sheath from the stent device. Preferably, the pullmember is embedded and sandwiched between the first layer and thereinforcement layer. Preferably, the pull member is embedded in the gluelayer. Embedding the pull member in the glue layer allows uniformtransfer of force while providing local strength. This manner ofattachment of the pull member to the outer sheath is sufficiently strongfor retraction of the outer sheath from the stent device, allows a lowprofile configuration and is easy to manufacture.

In one preferred embodiment, the preferred glue layer, the pull member,the first layer and the reinforcement layer coextend axially for adistance of at least about 1 inch (3 cm), at least about 2 inches (5 cm)or at least about 3 inches (8 cm). This feature of the first aspect ofthe present invention ensures a strong attachment of the pull member tothe outer sheath.

The above described first reinforcement layer of the outer sheath andthe above described attachment of the pull member to the outer sheathare applicable to both a pullback stent device delivery system and arolling membrane stent device delivery system. In the former system, thefirst layer is in sliding contact with the stent device and thepreferred glue layer and the reinforcement layer overlays the stentdevice. Pulling on the pull member will cause the first layer, thepreferred glue layer and the reinforcement layer to move axiallyrelative to the stent device in conjunction as a single laminarstructure. The first layer and the reinforcement layer are integrallyformed with one another. That is, the first layer and the second layerare formed from the same tube of material, which has been folded back onitself. Preferably, the pull member overlays the stent device andextends to a distal end of the stent device. This has been found tooffer an effective solution for ensuring successful pullback of theouter sheath.

In the latter delivery system, the outer sheath comprises an innerlayer, an outer layer and a fold-over portion connecting the inner layerand the outer layer, whereby axial movement of the outer layer relativeto the inner layer causes axial movement of the fold-over portionrelative to the stent device so that the fold-over portion can be movedproximal of the stent device in order to retract the outer sheath. Theouter layer includes the first layer, the preferred glue layer and thereinforcement layer. In a rolling system, necking of the outer layer,and the concomitant increase in radial friction forces, can cause theouter sheath to stick during retraction. Accordingly, it offersdeployment reliability to form the outer layer with the first layer, thereinforcement layer and the preferred glue layer. Preferably, the pullmember is attached to the outer sheath at the proximal portion of theouter sheath (the portion proximal of the transition portion) discussedabove in the rolling stent device delivery system.

The first layer and the reinforcement layer are preferably cold-drawnplastic layers. Such layers are thin, strong and easy to manipulateduring manufacturing of the stent device delivery system. Preferably,the plastic is polyethylene terephthalate (PET). This is a particularlyuseful material for the outer sheath of the first aspect of the presentinvention. Cold-drawing of the sheath during manufacture with the stentin place permits a reduced profile to be maintained. However, due to thereduced profile, such configurations are particularly susceptible to thenecking effect described earlier.

Preferably, the pull member is a pull wire. Preferably, the pull wire isflattened along at least a portion where it is embedded in between thefirst layer and the reinforcement layer. This ensures both a low profileconfiguration, an increased surface area for interaction with thelayers, and a strong attachment to the outer sheath.

The above described manner of attaching a pull member to an outer sheathof a stent device delivery system is also an independently applicablemodification to the prior art. Accordingly, in a second aspect of thepresent invention there is provided a stent device delivery systemcomprising a stent device and an outer sheath overlaying the stentdevice in a radially compact, delivery configuration of the stentdevice. The outer sheath is retractable relative to the stent device toallow radial expansion of the stent device to a deployed configuration.The outer sheath includes a first layer and a second layer that arelaminated together and preferably glued together by a glue layerradially between the first and second layers. A portion of the pullmember is attached to the outer sheath by positioning the portionradially between the inner and outer layers of the outer sheath.Preferably, the portion of the pull member is embedded in and glued bythe glue layer. This attachment of the pull member to the outer sheathallows a sufficiently strong attachment force, while avoiding measuresthat necessitate an increase in profile of the delivery system.

In a preferred embodiment, the pull member is positioned radiallybetween the first layer and the second layer of the outer sheath, andpreferably embedded in the glue layer, for an axial distance of at leastabout 1 inch (3 cm), at least about 2 inches (5 cm), or at least about 3inches (8 cm). A long attachment distance ensures a strong connection ofthe pull member to the outer sheath.

Preferably, the pull member is a pull wire. The pull wire is preferablyflattened at a distal end portion where the portion is embedded betweenthe inner and outer layer. This measure increases the attachment areawhile maintaining a low profile configuration.

Preferably, the first and second layers are made of a cold-drawnplastic, preferably a cold-drawn polyester material such as cold-drawnPET.

It is a preferred embodiment of the present invention to combine thefirst and second aspects. Thus, preferably the first layer of the secondaspect of the present invention is the first layer of the first aspectof the present invention and the second layer of the second aspect ofthe present invention is the reinforcement layer of the first aspect ofthe present invention.

In a third aspect of the present invention, there is provided a stentdevice delivery system comprising a stent device and an outer sheathoverlaying the stent device in a radially compact, deliveryconfiguration of the stent device. The outer sheath is retractable froma distal end of the stent device to a proximal end of the stent deviceto allow for radial expansion of the stent device to a deployedconfiguration. An inner catheter extends within a lumen of the stentdevice and provides a stent bed upon which the stent device is located.The stent bed defines an inwardly tapering profile, narrowing in radiusfrom a distal portion of the stent device to a proximal portion of thestent device.

The tapering profile of the stent bed, it is thought, induces a taperingprofile to the stent device, which is radially narrower at the proximalportion than the distal portion of the stent device. Necking typicallyoccurs in an extended interval during retraction. By allowing theproximal portion of the stent to be compressed to a greater extent thanthe distal portion, as the sheath retracts, the moving distal edge ofthe outer sheath progressively passes over a radially narrower profileof the stent device. This has consequently been found to reducedeployment force and also inhibits stent device deployment failure.

In a preferred embodiment, the stent bed tapers at a gradient (change inouter diameter of the stent bed divided by axial length over which thechange in outside diameter occurs) of 0.0003 to 0.005, preferably 0.0005to 0.002 and preferably 0.0006 to 0.0009. One way to calculate thegradient is to determine the largest outer diameter of the stent bedwhich will be at the distal portion of the stent device, and determinethe lowest outer diameter of the stent bed, which will be at theproximal portion of the stent device. A linear change from the largestoutside diameter to the smallest outside diameter can then be assumed inorder to determine the gradient. While in some embodiments, the taperingprofile is linear, other embodiments are envisaged, as below, where thechange in outer diameter occurs stepwise. One implementation couldinvolve the outer diameter changing by varying extents along the lengthof the stent device. The gradient is, in essence, an average gradient ofthe stent bed over the length of the stent device from the distalportion to the proximal portion.

In one embodiment, the stent bed is axially continuous with respect tothe stent device. The stent bed thus forms a continuously taperingprofile from the distal portion to the proximal portion of the stentdevice. In another embodiment, the stent bed is formed by a plurality ofaxially separated portions, such as axially separated band members. Inthe case of the use of axially separate band members, the bands have aprogressively reducing outside diameter in the proximal direction, whichpreferably involves a stepwise reduction from one band to an adjacentband in the proximal direction, where each band has a constant outsidediameter. Alternatively, the bands themselves can have an inwardlytapering outside diameter in the proximal direction. In both thecontinuous layer and separated band members embodiments, the stent bedmay taper in a step wise fashion and there may be 2, 3, 4, 5, 6 or moresteps. Thus, there may be 2, 3, 4, 5, 6 or more band members.

As well as, it is thought, inducing a tapering profile on the stentdevice, the stent bed also has a holding function for axially holdingthe stent device relative to the inner catheter. The stent bed ispreferably made of a compressible material and the stent device ispressed into the stent bed to deform the stent bed. The outer sheathmaintains the stent device partially embedded in the stent bed in thisway. This partial embedding provides a form fit resisting undesirableaxial movement of the stent device relative to the inner catheter.Further, the stent bed is preferably made of a tacky material, whichprovides a radial as well as an axial holding force on the stent devicerelative to the inner catheter. During expansion of the stent device,the stent device peels away from the tacky material of the stent bed.The use of both tacky and compressible materials for the stent bedprovides a combination of form fit and high strength axial lock tosecurely position the stent device in an axial direction, which willassist in correct positional deployment at the target diseased vascularlumen site. Suitable materials for the stent bed are rubber, siliconeglue or polyether block amide (PEBAX). Another example suitable materialis the glue sold under the trade name Dymax. The materials may besprayed on or coated on in some other way.

The stent bed is preferably formed as a layer on the inner catheter.

Preferably, the stent device delivery system comprises a pull member forputting in endwise tension to retract the outer sheath. The outer sheathpreferably comprises a distal portion overlaying the stent device, aproximal portion where the outer sheath is attached to the pull memberand a transition portion connecting the distal portion and the proximalportion, where the transition portion tapers inwardly from the distalportion to the proximal portion. Thus, the outer sheath is attached tothe pull member at a radially inward position as compared to the outsidediameter of the outer sheath at the distal portion overlaying the stentdevice. In such a pulling configuration, the pulling force is impartedto the outer sheath from a radially inward location. The taperingprofile of the stent bed is particularly useful in such configurationsfor reducing deployment force and increasing deployment reliability.

The tapering profile is particularly useful when applied to a rollingstent device delivering system. Thus, in a preferred embodiment, theouter sheath comprises an inner layer, contacting an outer surface ofthe stent device, an outer layer and a fold-over portion connecting theinner layer and the outer layer. Proximal movement of the outer layerrelative to the inner layer will cause the fold-over portion to moveproximally axially relative to the stent device and thus enablesretraction of the outer sheath. The tapering profile of the stent bedcan yield an ever increasing ease of sliding between the inner layerproximal portion still on the stent device and the outer layer slidingpast it proximally to ease any tendency for sticking of the rollingmechanism. It is thought that undulations on the outer surface of thestent device, perhaps in combination with necking of the outer sheath,has, in the past, caused sticking of the rolling mechanism, whichincreases the deployment force and can cause deployment failure. It isbelieved that the increased gap provided by the tapering profilealleviates or avoids such difficulties.

The tapering profile is also applicable to a pullback stent devicedelivery system. In such a system, the outer sheath slides over thestent device from a distal end to a proximal end during retraction asthe pull member is put under endwise tension. In one embodiment, theouter sheath comprises a first layer and a second or reinforcement layerthat are laminated together, preferably by a glue layer radially betweenthe first and second layers so that the first layer, the preferred gluelayer and the second layer are moved axially in conjunction relative tothe stent device to retract the outer sheath. Even if the inner layerand the outer layer are made of a neckable plastic material, which canadvantageously be made thin, the tapering profile allows a small amountof necking of the outer sheath towards a proximal end of the stentdevice to not cause sticking of the outer sheath during retraction.

Preferably, the outer sheath is formed having a tapering profilefollowing the tapering profile of the stent bed. “Following” the taperhere means tapering in the same direction. Preferably, the outer sheathalso tapers at the same gradient as the stent bed. The manner in whichthis is achieved is described below. Having the outer sheath tapered inthis way reinforces the advantages of reducing stent deployment forceand increasing stent deployment reliability. Similarly, it is thought,the stent device is preferably forced to share the tapering profile ofthe stent bed by compression against the tapering stent bed and by thetapering profile of the outer sheath. The outer sheath may be formedhaving a tapering profile in a region enclosing the stent, or the taperof the outer sheath may extend substantially beyond the region enclosingthe stent device.

In one embodiment, the outer sheath is formed by folding a sleeve ofmaterial, preferably plastic, back onto itself so as to define the innerlayer and the outer layer of the outer sheath in the rolling systemdescribed above or the first layer and the second layer in the pull backsystem described above. Glue can be applied between the first and secondlayers or the first and second layers can be laminated together to formthe pull back stent device delivery system discussed above or the innerand outer layers can be allowed to move relative to one another toprovide the rolling stent device delivery system discussed above.Preferably, the sleeve of material is formed into the tapered profile ofthe outer sheath including the portion of the sleeve that will form theinner or first layer and the portion of the sleeve that will form theouter or second layer. This provides an outer sheath having an inner orfirst layer tapering inwardly from the distal portion to the proximalportion of the stent device and an outer or second layer that tapersoutwardly from the distal portion to the proximal portion of the stentdevice, thereby further increasing the potential gap between theselayers to avoid sticking during retraction of the outer sheath. Theouter sheath is preferably made of a cold-drawn plastic material. Thecold-drawn plastic material is formed into the tapered profile bycold-drawing over a tapered mandrel as described below.

The features of the first, second and third aspects of the presentinvention are combinable. Thus, features of the stent device deliverysystem described with respect to any one of the first to third aspectsof the present invention may be combined with the stent device deliverysystem of any one of the other aspects of the present invention.

In a fourth aspect of the present invention, there is provided a methodof making a stent device delivery system. The method comprises a step ofloading the stent device into a sleeve of plastic material. The methodfurther comprises a step of positioning an inner catheter into a lumenof the stent device. The inner catheter presents a stent bed for thestent device to be located upon. The stent bed has a tapering profile.The method yet further comprises a step of cold-drawing the sleeve withthe stent device loaded therein and located on the stent bed to reducethe diameter of the sleeve, and thus the stent device, to engage thestent device and the stent bed and put the stent device into a reducedprofile, delivery configuration. The sleeve provides an outer sheath ofthe stent device delivery system that is retractable relative to thestent device to allow the stent device to radially expand to a deployedconfiguration.

Cold-drawing of the outer sheath according to the above method forcesthe stent device onto the stent bed, which will, it is thought, inducethe tapered profile of the stent bed to the stent device. Further, theouter sheath will be cold-drawn to share this tapered profile. Thebenefits of this tapered profile have been discussed above. Cold-drawingthe stent also permits the overall profile of the delivery system to beadvantageously reduced by a combination of enhanced stent compressionand reduced sheath radial thickness.

The sleeve of plastic material may be folded back onto itself to providethe outer sheath with a first layer, a second, outer layer and a distalfold-over portion connecting the first layer and the second layer. Thefirst layer and the second layer may be laminated together, preferablyby a glue layer, in providing a pullback stent device delivery system.Alternatively, the inner layer and the outer layer may be left movablerelative to one another to provide a rolling stent device deliverysystem whereby the first, inner layer and the second, outer layer areable to be moved relative to one another to cause the fold-over portion(rolling edge) to move relative to the stent device thereby allowingretraction of the outer sheath, and the stent to be radially expanded.

The tapering profile of the stent bed tapers inwardly from a distalportion of the stent device to a proximal portion of the stent device.The terms distal and proximal in this instance are to be understood withrespect to the distal fold-over portion.

In a preferred embodiment, a mandrel is positioned within the sleeve ofplastic material at a distal end of the stent device. The mandrel has atapering profile that continues the tapering profile of the stent bed.The sleeve of plastic material is cold-drawn onto the mandrel, whichprovides a cold-drawn portion overlaying the stent device and acold-drawn extension portion overlaying the mandrel. The extensionportion is folded back over the stent device portion to provide a first,inner layer of the outer sheath and a second, outer layer of the outersheath. When folded back, the second layer defines a reversely directedtapering profile, which increases a gap between the first layer and thesecond layer, which reduces the chances of sticking of the outer sheathduring retraction of the outer sheath from the stent device.

The method can be further defined so as to provide the features of thestent device delivery system according to the above first, second, andthird aspects of the invention and to provide features of thehereinbelow described further aspects of the present invention.

In a fifth aspect of the present invention, there is provided a stentdevice delivery system comprising a stent device and an outer sheathoverlaying the stent device in a radially compact, deliveryconfiguration of the stent device. The outer sheath is retractable toallow the stent device to radially expand to a deployed configuration.The stent device delivery system comprises a pull member for pullingproximally on to retract the outer sheath. A portion of the outer sheathis heat shrunk radially onto a relatively heat shrink resistant supportmember in order to capture a distal portion of the pull member radiallybetween the outer sheath and the heat shrink resistant support member.

This aspect of the present invention offers a strong connection of thepull member to the outer sheath by making use of heat shrink material,which after heat shrinking, provides a compressive force on the pullmember between the heat shrunk material and the support member. Further,without the features of the present aspect of the invention, the portionof the outer sheath that connects to the pull member is potentiallysubject to failure. In the present aspect of the invention, this portionis strengthened by heat-shrinking, which enhances the materialproperties of the heat shrink sheath. The support member is resistant toheat-shrinking, i.e. does not substantially change its properties at therelevant heat shrink temperature, compared to the portion of the outersheath that has been heat shrunk. In use, the pull member is subjectedto a proximal pulling force, which moves the pulling member, the outersheath and the support member proximally with respect to the stentdevice to retract the outer sheath.

Preferably, the captured portion of the pull member extends an axialdistance of at least about 1 inch (3 cm), at least about 2 inches (5cm), or at least about 3 inches (8 cm). Preferably, the captured portionof the pull member defines a flattened profile with respect to theradial direction. These features both contribute to providing a strongattachment between the pull member and the outer sheath.

The portion of the outer sheath is heat shrunk onto the heat shrinkresistant support member at an axial portion of the outer sheath that isproximal of the stent device. Exposing the stent device to heat, such asthe heat required to heat shrink the outer sheath, is to be avoidedespecially in cases where the stent is manufactured from shape-memoryalloys such as Nitinol. Similarly, exposing cold-drawn polymers, such asmay be used to encapsulate the stent device, the heat will tend tonegate the beneficial physical properties achieved by the cold-drawingprocess. By positioning the heat shrunk attachment of the pull memberproximally of the stent device, a distinction can be made between aso-called “hot side” of the stent device delivery system that isproximal of the stent device and a so-called “cold side” of the stentdevice delivery system that consists of the remaining distal portionthereof.

The heat shrunk portion of the outer sheath provides a transitionportion connecting the heat shrunk portion to a distal portion of theouter sheath overlaying the stent device. The transition portion tapersinwardly from the distal portion to the heat shrunk portion.Accordingly, a low profile heat shrunk portion, in which portion thepull member is attached to the outer sheath, is provided, which willallow it to be received in a sufficiently low profile delivery shaftextending back to a handle, control portion or access portion of thestent device delivery system. A transition section and a low profileportion proximal of it has, in prior art designs, provided a relativelylower strength area of the outer sheath, which has in turn led todeployment failure. The present invention provides heat shrunk materialin this area to inhibit such possible failures.

In a preferred embodiment, the fifth aspect of the present invention iscombined with the first aspect of the present invention, resulting in apull member that is strongly attached to the outer sheath in a mannerthat is relatively simple to manufacture and forming a low profile stentdevice delivery system. More specifically, the outer sheath comprises afirst layer and a reinforcement layer that are laminated together,preferably by a glue layer. The captured portion of the pull member ispositioned radially between the first layer and the reinforcement layer,preferably embedded in and retained by the glue layer. The first layerand the reinforcement layer are heat shrunk onto the heat shrinkresistant support member to capture the pull member radially between theouter of the two layers and the support member. Compression of the gluelayer and pull member by the heat shrunk first layer and reinforcementlayer enables an advantageously reduced profile to be obtained and, byreducing the thickness of any glue layer, enhances the bond strengthbetween these elements.

The fifth aspect of the present invention can be applied to a rollingstent device delivery system. The outer sheath comprises an inner layer,an outer layer and a fold-over portion connecting the inner layer andthe outer layer. The fold-over portion is axially movable relative tothe stent device by moving the inner layer relative to the outer layer,thereby allowing the outer sheath to be retracted from the stent device.The outer layer is heat shrunk onto the heat shrink resistant supportmember to capture the pull member. Preferably, the outer layer includesthe above-mentioned first layer and reinforcement layer laminatedtogether, preferably by a glue layer. The first layer and thereinforcement layer are heat shrunk onto the heat shrink resistantsupport tube to capture the pull member. As stated above, the heatshrunk portion of the outer sheath and the captured portion of the pullmember are positioned proximal of the stent device.

Preferably, the pull member is a pull wire, which is further preferablyflattened at the captured portion.

In the rolling stent device delivery system, the inner layer is fixedrelative to an inner catheter at a position proximal of the stentdevice. The outer layer is, in use, moved proximally relative to theinner layer to cause the fold-over portion to progressively approach thefixed proximal end of the inner layer during retraction of the outersheath. In a preferred embodiment, a proximal end of the inner layer isheat shrunk radially onto the inner catheter to fix it thereto. Thismakes use of the previously-described concept of defining a “hot side”of the stent device delivery system where materials can be heat-shrunk,distinct from a “cold side”. Heat shrinking offers a convenient, interms of manufacturing, method of fixing the pull member to the outersheath and the proximal end of the inner layer to the inner catheter.

Preferably, the proximal end of the inner layer of the outer sheath,which is fixed relative to the inner catheter, peels away under apulling force as the fold-over portion, which defines the rolling edge,meets it and is pulled further proximally during retraction of the outersheath. Heat shrink attachment of the inner layer to the inner catheter,relying on radial compression rather than adhesion to fix the innerlayer to the inner catheter, is able to provide an appropriate peelforce, low enough to allow the inner layer to come away from the innercatheter during retraction of the outer sheath, yet strong enough tootherwise, in use, stay fixed relative to the inner catheter.

The stent device is held fixed relative to the inner catheter by aholding mechanism presented by the inner catheter. Preferably, theholding mechanism is, at least in part, a stent bed according to thethird aspect of the present invention described above.

A suitable material for the heat resistant support member is polyimide.A suitable heat shrinkable material for the outer sheath is polyethyleneterephthalate (PET).

The generally described features of the fifth aspect of the presentinvention are combinable with any one or more of the features of thefirst to fourth aspects of the present invention in accordance with thecorresponding combination of features given in the first, second andthird embodiments of the present invention described in detail in thefollowing.

In a sixth aspect of the present invention, there is provided a methodof making a stent device delivery system. The method comprises providinga stent device and an outer sheath overlaying the stent device in aradially compact delivery configuration of the stent device, wherein theouter sheath is retractable to allow the stent device to radially expandto a deployed configuration. The method further comprises a step ofproviding a pull member for attachment to the outer sheath to besubjected to a proximal pulling force to effect retraction of the outersheath. The method yet further comprises a step of positioning arelatively heat shrink resistant support tube within the outer sheath,at a position axially proximal of the stent device. The method even yetfurther comprises a step of radially heat shrinking a portion of theouter sheath onto the support tube to capture the pull member radiallybetween the outer sheath and the support tube.

In a preferred embodiment, the method further comprises forming theouter sheath to include a first layer and a reinforcement layer. Themethod comprises a step of laminating the reinforcement layer to thefirst layer to retain the pull member radially between the first layerand the reinforcement layer. Preferably, the first layer is glued to thereinforcement layer and the pull member is embedded in a glue layergluing the first layer and the reinforcement layer together. The firstlayer and the reinforcement layer are heat shrunk onto the support tubeas described above to capture the pull member radially between the outersheath layer and the support tube.

Preferably, the method further comprises loading a stent device into asleeve of material for forming the outer sheath. The sleeve of plasticmaterial is cold-drawn to reduce the diameter of the sleeve and toreduce the diameter of the stent device to put the stent device in theradially compact, delivery configuration. The stent device is thusprovided with an outer sheath overlaying the stent device in a radiallycompact, delivery configuration. The outer sheath is retractable toallow the stent device to expand to a radially expanded, deployedconfiguration. In a preferred embodiment, the sleeve of plastic materialis cold-drawn by application of endwise tension onto a mandrelpositioned at a distal end of the stent device to provide a firstportion of cold-drawn sleeve overlaying the stent device and anextension portion of cold-drawn sleeve overlaying the mandrel. Theextension portion is folded back onto itself to overlay the stent deviceso that the outer sheath comprises an inner layer comprising the firstportion, an outer layer formed by the extension portion and a fold-overportion connecting the inner layer and the outer layer, therebyproviding a rolling stent device delivery system.

A proximal end of the sleeve of plastic material is fixed to the innercatheter by heat shrinking the inner layer thereto at a position axiallyproximally of the stent device, that is to say at a position opposite toa distal end of the stent device where the fold-over portion will belocated.

After folding the sleeve of material onto itself to form the inner layerand the outer layer as described above, the reinforcement layer, being afurther sleeve of plastic material, is placed coaxially over the interimouter layer of the outer sheath and laminated, preferably glued, theretoto form an outer layer having a first layer and a reinforcement layerthat are laminated together, preferably by a glue layer radiallypositioned therebetween. The outer layer comprising the first layer, thepreferred glue layer and the reinforcement layer is heat shrunk onto thesupport tube at a position axially proximal of the stent device with thepull member embedded between the first layer and the reinforcementlayer, preferably embedded in the glue layer, thereby capturing the pullmember radially between the outer sheath and the support tube asdescribed above.

The stent bed and optionally the mandrel may have a tapered profile andthe stent device delivery system may be produced in accordance with thedescription given above for the fourth aspect of the present invention.Further, the method may be configured to produce features of the systemsof any one or a combination of the first, second, third and fifthaspects of the present invention.

There are generally applicable features of the present invention, in anyof its aspects, that have yet to be described.

The stent device delivery system preferably comprises a tip at a distalend thereof. The tip may taper inwardly in a distal direction in orderto ease insertion into narrow passages. The tip preferably comprises anannular notch for stationing the fold-over portion.

Preferably, the outermost layer of the outer sheath is hydrophilic.Preferably, it is the outer surface of the reinforcement layer that ishydrophilic. The purpose of this is to ease passage of the stent devicedelivery system during delivery to provide a lubricated distal surfaceof the system for ease of passage during delivery.

The provision of an outermost layer of an outer sheath of a stentdelivery system is an independently applicable modification to the priorart. Thus, it is disclosed to have a stent device delivery systemcomprising a stent device and an outer sheath overlaying the stentdevice in a radially reduced, delivery configuration. The outer sheathis retractable to uncover the stent device to allow the stent device toexpand radially to a deployed configuration. An outermost surface of theouter sheath is hydrophilic along at least a distal axial portionthereof overlaying the stent device.

Preferably, the stent device is a self-expanding stent device.Self-expanding stent devices are biased from the delivery configurationto the radially expanded, deployed configuration at body temperature.Suitable self-expanding stent devices for application in the presentinvention are well-known to the skilled person, and may be manufacturedfrom shape-memory alloys, such as Nitinol.

In the case of a self-expanding stent device, the radially reduced,delivery configuration is a radially compressed, delivery configuration.The outer sheath restrains the stent device in the radially compressed,delivery configuration. Retraction of the outer sheath releases thestent device to self-expand to the radially expanded, deployedconfiguration.

The present invention will be further understood from the detaileddescription of the first, second and third stent device delivery systemgiven below. The detailed description will also be useful for theskilled person in providing guidance, although without limitation as tothe combinability of the various features of the various aspects of thepresent invention given above.

The laminate of the first layer and the reinforcement layer are thinnerthan state of the art outer sheaths. The first layer and thereinforcement layer are both between 30 and 40 μm thick in the radialdirection. Preferably, the resulting laminate is less than 100 μm thick,preferably between 70 and 90 μm. Despite this reduced thickness, thelaminate maintains the required strength characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a stent device delivery system of the pullback type, wherethe axial portion of the outer sheath overlaying the stent device isformed from a lamination of first and second layers of polymericmaterial. A pull wire is embedded radially between the first and secondlayers and extends to the distal end of the outer sheath.

FIG. 2 shows a view of the stent device delivery system of FIG. 1whereby the stent device delivery system is rotated by 90° if one takesthe proximal to distal direction as pointing to the clock face. Thisparticular cross-section shown allows the pull member to be clearlyviewed.

FIG. 3 shows a stent device delivery system of the type having a rollingouter sheath. Further, the pull member is attached to an outer layer ofthe outer sheath at a position proximal of the stent device bylaminating a first layer of polymeric material to the outer layer andsandwiching the pull member radially therebetween.

FIG. 4 shows another stent device delivery system of the rolling kindhaving an outer sheath that is retracted by rolling an outer layer overan inner layer. Further, a reinforcement layer is laminated to the outerlayer, which reinforcement layer extends axially from a positionproximal of the stent device to a position overlaying the stent device.The pull member is attached to the outer layer of the outer sheath bybeing sandwiched radially between the outer layer and the reinforcementlayer in the lamination of these two layers. The stent device deliverysystem includes a heat shrink resistant support tube and the outer layeris heat shrunk onto the heat shrink support tube. The heat shrinksupport tube is positioned proximally of the stent device.

FIG. 5 shows a view of the stent device delivery system of FIG. 4 thathas been rotated 90° clockwise and in a particular cross-section tobetter show the pull member.

FIG. 6 shows a tapering stent bed design. The tapering stent bed is alsoshown in the system of FIGS. 1 to 4. The tapering stent bed iscontinuous from a radially larger distal end to a radially smallerproximal end.

FIG. 7 shows an alternative design for a tapering stent bed, which ismade up of axially separated band members, where the band members reducein thickness from a distal end of the stent bed so as to define atapering stent bed.

DETAILED DESCRIPTION

A first stent device delivery system 1 is shown in FIGS. 1 and 2. Thestent device delivery system 1 comprises an inner catheter 3 having astent bed 5 mounted on the inner catheter 3. A stent device 4 is clampedonto the stent bed 5 so that the inner surface of the stent device 4engages with the outer surface of the stent bed 5. An outer sheath 2extends over the stent device 4 to constrain the stent device 4 in theradially reduced, delivery configuration shown, where the inner surfaceof the stent device 4 engages the outer surface of the stent bed 5. Theouter sheath 2 is retractable relative to the inner catheter 3 and thestent device 4, and thus to position an end of the outer sheath 2, whichis a distal end of the outer sheath 2, proximally of the stent device 4to a retracted position. The retracted position of the outer sheath 2frees the stent device to expand radially from the deliveryconfiguration shown to a deployment configuration for supporting adiseased vascular lumen. The stent device shown is preferably aself-expanding stent device and moves to the deployed configuration,once the outer sheath 2 is retracted, by material memory. As the outersheath 2 is retracted, the stent bed 5 serves to hold the stent device 4axially stationary relative to the inner catheter 3. The stent bed 5 isaxially distributed along the inner surface of the stent device 4 fromabout a proximal end to about a distal end of the stent device 4 toensure a sufficient holding force to resist the outer sheath 2 causingaxial displacement of the stent device 4 relative to the inner catheter3. Other means for holding the stent device 4 relative to the innercatheter, such as a stop proximal of the stent device, are known in theart and would be suitable for this purpose.

The outer sheath 2 is made from a polymeric material comprising a first,outer layer 10 and a second, inner layer 9 acting as a reinforcementlayer 9. A glue layer 11 is radially interposed between the first layer10 and the reinforcement layer 9. The first layer 10 and thereinforcement layer 9 are laminated to one another by the glue layer 11sandwiched radially therebetween. The glue layer 11 is distributedcircumferentially around the outer sheath 2. The laminated first andreinforcement layers 9, 10 extend from about a proximal end of the stentdevice to about a distal end of the stent device. In fact, in the system1 shown, the first and second layers 9, 10 extend beyond a distal end ofthe stent device 4. Connecting the first and second layers 9, 10 is afold-over portion 12 at the distal end of the outer sheath 2. An innersurface of the reinforcement layer 9 is in contact with an outer surfaceof the stent device 4.

A pull member 7 for retracting the outer sheath 2 is positioned radiallybetween the laminated first and reinforcement layers 9, 10 of the pullmember 7 at a distal end portion of the pull member 7. The glue layer11, which adheres the first and reinforcement layers 9, 10 together isspread along the distal portion of the pull member 7 and contacts thepull member 7 to adhere the first and reinforcement layers 9, 10 of theouter sheath 2 to the distal portion of the pull member 7 as well as toeach other. The pull member 7 is a wire in the shown embodiment that hasbeen flattened along the distal portion as compared to a proximalportion of the pull member 7, which is cylindrical. The distal portionof the pull member 7 extends along the stent device 4 from a proximalend to a distal end of the stent device 4 and in the shown system 1, toa distal end of the outer sheath 2.

FIGS. 1 and 2 also show a tip member 6 attached to the inner catheter 3.The tip member 3 has a recess 13, which receives a distal end of theouter sheath 2. The tip member 6 has a middle, in the axial direction,section that is of the same diameter as the outer sheath 2 and tapersradially inwardly towards the distal end of the tip member 6. In FIG. 1,the inner catheter 3 can be seen as a simple tube in the axial portionwhere the stent bed 5 and the stent device 4 is located. At a positionproximal of the stent device 4, the simple tube of the inner catheter 3is connected to a guide portion 8 of the inner catheter 3 that comprisesan inner tube and a tubular sleeve overlaying the inner tube, where theinner tube has formed through the wall thickness a plurality of axiallydistributed slits formed so that the extent of each slit in thecircumferential direction exceeds half of the circumference of the tubeto allow the guide portion of the inner catheter to be flexed. Theconfiguration of the guide portion of the inner catheter is the subjectof International Patent Application No. PCT/EP2010/060559, which isincorporated by reference in its entirety into this application. Theguide portion 8 of the inner catheter 3 will not be described in furtherdetail in the present application. A suitable material for the simpletube portion of the inner catheter 3 is polyamide.

Lamination of the first and reinforcement layers 9, 10 by the glue layer11 allows the outer sheath 2 to be made from polymeric first andreinforcement layers 9, 10. Usually, and particularly for long stentdevices, this would mean that the outer sheath 2 would be stressed tofailure or necking as the outer sheath 2 moves over the stent device 4because of the drag force between the inner surface of the outer sheath2 and the outer surface of the stent device 4. Necking of the outersheath 2 could also cause failure of the outer sheath 2 duringretraction because it would too tightly grip the stent device 4, whichwould cause a required retraction force greater than the breakingstrength of the outer sheath 2. The combination of first andreinforcement layers 9, 10 and a means for laminating the first andreinforcement layers 9, 10 together has been found to be surprisinglyresistive to necking of the outer sheath 2 during retraction of theouter sheath 2 as well as to provide strength benefits beyond the merecombination of the layers 9, 10.

The outer sheath 2 is an integral structure in that the first layer 9and the second layer 10 are made from the same tube of material, whichis folded back upon itself and glued together to form the reinforcementlayer 9, the first layer 10 and the connecting portion 12 between thefirst. The outer sheath 2 includes a transition portion 14 connecting adistal axial portion 16 of the outer sheath 2, overlaying the stentdevice 4, and a proximal portion 15. The transition portion 14 tapersinwardly from the distal portion 16 to the proximal portion 15, as theproximal portion 15 has a radially reduced configuration as compared tothe distal portion 16. This allows the radial bulk of the stent device 4to be accommodated at the distal portion and allows a reduced profileguide portion at the proximal portion 15. The transition portion 14 isparticularly susceptible to failure during retraction of the outersheath 2. Accordingly, in an alternative to that shown in FIGS. 1 and 2,the reinforcement provided by the laminated first and reinforcementlayers 9, 10 can extend proximally beyond that shown so that thelaminated first and reinforcement layers 9, 10 form the outer sheath inthe distal portion 16 as well as the tapering portion 14 and/or at leastsome of the proximal portion 15.

The stent bed 6 shown in FIGS. 1 and 2 has a tapering profile from alarger outside diameter distal end to a smaller outside diameterproximal end. Receiving the stent device 4 on such a stent bed 5 isadvantageous for reasons discussed further below. Examples for thetapering profile of the stent bed can be seen in FIGS. 6 and 7. In FIG.6, the stent bed is formed by a continuous layer applied to the innercatheter 3. The stent bed 5 has a thicker profile at one end, the distalend, than at the other end, the proximal end, of the stent bed 5. In theembodiment shown, the stent bed 5 tapers radially inwardly in a linearfashion from the distal end to the proximal end. The layer could,however, reduce in thickness in the radial direction in a stepwisefashion or in some other non-linear curved arrangement, such as in anexponential fashion. In FIG. 6, the outside diameter of the stent bed 5is 1.4 mm at the distal end and 1.2 mm at the proximal end and has anaxial length of 220 mm. A gradient for the tapering profile can beworked out by taking the maximum change in thickness over the length ofthe stent bed 5 and dividing this value by the length of the stent beds,which gives (1.4−1.2)/220=0.00091, or 0.091%.

In FIG. 7 an alternative arrangement for the stent bed 5 is shown. Thestent bed 5 is formed by a plurality of axially separated band members17. The band members 17 thus define axially distributed gaps betweeneach pair of band members 17 in the stent bed 5. In the embodiment ofFIG. 6, there are five band members 17, but the use of more band membersor indeed one or two fewer band members is envisaged as beingfunctional. Each band member 17 has a constant outer diameter while theset of band members 17 reduce progressively in thickness from the distalend to the proximal end. Each band member 17 may have a constantthickness as shown so as to define a constant outside diameter for thestent bed 5 along the axial portion where the band member 17 is located.Alternatively, each band member 17 could itself define a taperingprofile. This tapering profile could follow a linear path from thedistal end of the stent bed 5 to the proximal end. In another variation,each band member 17 could itself define a tapering profile following astepwise or non-linear path. In the example of FIG. 7, the most distalband member 17 defines an outside diameter for the stent beds of 1.4 mm,the second most distal band member 17 defines an outside diameter forthe stent beds of 1.35 mm, the middle band member 17 defines an outsidediameter for the stent beds of 1.30 mm, the second most proximal bandmember 17 defines an outside diameter of 1.25 mm and the most proximalband member defines an outside diameter of 1.20 mm. The stent bed 5extends over an axial length of 230 mm. Accordingly, the gradient of thetapering profile of the stent bed 5 is (1.4−1.2)/230=0.00087, or 0.087%.Other lengths of stent beds are envisaged from 100 mm to 350 mm, forexample. A range of maximum change in the outside diameter of the stentbed 5 could be from 0.1 mm to 0.4 mm, for example. The earlier givenranges for the gradient of the tapering profile of the stent bed 5 arepreferred, and particularly gradients in the range 0.01% to 0.1%, morepreferably 0.05% to 0.1%, are desirable.

The stent bed 5 of FIG. 6 could be made by spraying rubber or siliconeglue onto the inner catheter 3. A Dymax medical adhesive layer for thestent bed 5 is also envisaged. In the example of FIG. 7, the stent bed 5may be formed by polyether block amide (PEBAX) or a Dymax adhesive. Theband members 17 are preferably formed on the inner catheter 3, ratherthan formed separately and slid over the inner catheter 3 into position.These materials are chosen because they offer a tacky and deformablestent bed 5 for receiving the stent device 4. The tacky stent bed 5provides a slight radial force against expansion 4. The stent bed 5 willnaturally provide an axial holding force for the stent device 4 relativeto the inner catheter 3 by friction between the stent device 4 and thestent bed 5. Further, the deformability of the stent bed 5 allows thestent device 4 to be partially embedded into the outer surface of thestent bed 5, which will provide a form fit between the stent device 4and the stent bed 5, which further ensures a sufficient hold of thestent device 4 relative to the inner catheter 3. The use of a stent bed5 that is distributed along an inner surface of a stent device 4 from aproximal end to a distal end of the stent device 4 and having tackinessand deformability properties is discussed in WO 2010/031755, which isincorporated by reference in its entirety into this application. Thestent bed 5 may be non-tapered in accordance with stent beds known inthe art such as in WO 00/71058, which is incorporated by reference inits entirety into this application. In another alternative, a pushelement proximal of the stent device 4 may be used to hold the stentdevice 4 relative to the inner catheter 3. Such a proximal push elementis disclosed in FIGS. 1 and 2 of WO 00/71058, for example.

The tapered profile design for the stent bed 5 is advantageous for thefollowing reasons. In a pullback outer sheath design as shown in FIGS. 1and 2, the retraction force or the drag between the outer sheath 2 andthe stent device 4 is at its greatest when relative movement between thestent device 4 and the outer sheath 2 begins. The larger diameterportion of the stent bed 5 is more strongly compressed by the stentdevice 4 than the smaller diameter proximal portion and thus provides agreater holding force towards the distal end of the stent device 4.Also, the larger diameter portion pushes the stent device 4 morestrongly into the outer sheath 2, causing a greater drag force betweenthe stent device 4 and the outer sheath 2 at the distal end. Thetapering profile of the stent bed 5 is believed to provide sufficientholding force at the distal end, where it is needed most, while thereducing diameter lessens the overall drag force between the stentdevice 4 and the outer sheath 2 as a whole, as compared to if the stentbed 5 had a constant diameter equal to the outside diameter of the stentbed 5 at the distal end. Accordingly, the force required to retract theouter sheath 2 is reduced overall, while ensuring sufficient holding ofthe stent device 4 relative to the inner catheter 3 for a correctplacement of the stent device 4 at the target site. The reduceddeployment force allows thinner polymeric materials to be used for theouter sheath 2 to contribute to a reduced profile design of the stentdevice delivery system 1.

Returning to the stent device delivery system 1 shown in FIGS. 1 and 2,deployment of the stent device 4 will be described. A guidewire is firstfed through the tortuous passageways of the vasculature of a patient soas to arrive at the site of the diseased vascular lumen that requiressupport by a stent device 4. The stent device delivery system 1 of FIGS.1 and 2 is then fed along the guidewire by the guidewire being receivedin a lumen of the inner catheter 3. The tapering profile of the nozzle 6aids delivery because it provides a smooth distal surface for easingpassage of the stent device delivery system 1 through the vasculature ofthe patient. A correct position of the stent device delivery system 1 atthe target site is determined by radioimaging, making use of aradiopaque material positioned at the distal and proximal ends of thestent device 4. In order to deploy the stent device 4, the surgeonoperates a hand-held portion of the system 1 to cause the pull member 7to be pulled back relative to the stent device 4.

As the pull member 7 is caused to move proximally, the first andreinforcement layers 9, 10 of the outer sheath 2 move as a singlelaminar structure relative to the stent device 4. Axial movement of theouter sheath 2 relative to the stent device 4 causes the inner surfaceof the outer sheath 2 to drag over the stent device 4. This drag forcetends to force the stent device 4 in the proximal direction relative tothe inner catheter 3. The engagement between the outer surface of thestent bed 5 and the inner surface of the stent device 4 resists anyproximal movement of the stent device 4 to hold the stent device 4 fixedrelative to the inner catheter 3. As the distal end or connectingportion 12 of the outer sheath 2 moves over the stent device 4, thestent device 4 is released from the outer sheath 2 progressively in aproximal direction.

The stent device 4 when released expands radially from its deliveryconfiguration shown in FIGS. 1 and 2 to a deployed configuration forsupporting the diseased vascular lumen. The stent device 4 is fullydeployed once the distal end of the outer sheath 2 is positionedentirely proximally of a proximal end of the stent device 4, which iswhen the outer sheath is considered retracted from the stent device 4.Extending the pull member 7 so as to overlay the stent device 4 and beattached to the outer sheath 2 at a location distal of the transitionsection 14 of the outer sheath 2 reduces the chance of failure of theouter sheath 2 because the pull member 7 greatly contributes to theaxial strength of the outer sheath 2. The further the pull memberextends distally relative to the outer sheath 2, the greater axialdistance the outer sheath is reinforced by the pull member 7. Hence, inthe preferred configuration shown in FIGS. 1 and 2, the pull member 7extends to the distal end of the outer sheath 2. The lamination of thefirst and reinforcement layers 9, 10, particularly by use of a gluelayer 11 as shown, provides necking resistance for the outer sheath 2and also axial strength to avoid sticking of the outer sheath 2 on thestent device 4 and potential failure of the outer sheath 2 duringretraction.

In an alternative to that shown in FIGS. 1 and 2, the pull member 7 maybe attached at a position proximal of the stent device 4 and proximal ofthe transition section 14 of the outer sheath 2. In this arrangement,the reinforcement layer 9 would be extended also proximal of the stentdevice 4 so that the pull member 7 is still attached by laminationradially between the first layer 10 and the reinforcement layer 9. Theouter sheath would not then be reinforced by the pull member 7 along anaxial portion where the stent device 4 is located, which would mean thatthe distal portion 16 of the outer sheath 2 must be sufficiently strongto manage the axial forces during retraction without necking, stickingor breaking. The reinforcement to the first polymeric layer 10 of theouter sheath 2 provided by the lamination with the reinforcement layer 9and preferably also the glue layer 11 thus takes on particularimportance in this alternative arrangement. This alternative could befurther modified by heat shrinking the first layer 10 and thereinforcement layer 9 onto a heat shrink resistant support tube locatedaxially within the proximal portion 15 of the outer sheath. The pullmember 7 would still be located radially between the first layer 10 andthe reinforcement layer 9. Heat shrink attachment, as well as attachmentby lamination, of the pull member 7 ensures secure attachment of thepull member 7 to the outer sheath 2. Such heat shrink attachment isdiscussed further below with respect to FIGS. 4 and 5.

FIG. 3 shows another exemplary stent device delivery system. Where likeelements are referred to, the same reference numeral has been used as inFIGS. 1 and 2.

The stent device delivery system 30 of FIG. 3 has an outer sheath 22 ofthe rolling kind. As before, a stent bed 5 having a profile taperingradially inwardly from a distal end to a proximal end is mounted to aninner catheter 3. A stent device 4 overlays the stent bed 5 and theinner surface of the stent device 4 engages with the outer surface ofthe stent bed 5 to provide an interaction holding the stent device 4relative to the inner catheter 3. In a distal portion 36 of the outersheath 22 overlaying the stent device 4, the outer sheath 22 is formedinto an outer layer 39 that is folded over an inner layer 38 andconnected by a fold-over portion 40. The outer layer 39 is axiallymoveable relative to the inner layer 38 in a proximal direction, whichcauses the fold-over portion 40 to roll proximally, thereby effectingretraction of the outer sheath 22. The inner layer 38 is attached to theinner catheter 3 at a location proximal of the stent device 4.

The outer layer 39 extends proximally beyond the inner layer 38 toprovide a proximal portion 35 of the outer sheath 22 that is attached toa pull member 27. The pull member 27 is attached to the outer sheath 22by lamination with a reinforcement layer 29. The pull member 27 iscaptured radially between the laminated outer layer 39 and thereinforcement layer 29. The reinforcement layer 29 is, in system 30shown in FIG. 3, located radially inwardly of the outer layer 35 of theouter sheath 22. The reinforcement layer 29 could, however, be disposedoutwardly of the outer layer 34 of the outer sheath 22. The outer layer39 and the reinforcement layer 29 are laminated together by a glue layer31 distributed circumferentially around and axially along thereinforcement layer 29. The pull member 27 is embedded in the glue layer31, which provides an adhesive connection to the reinforcement layer 29and the outer layer 39 as well as a connection by the capturing effectof the laminated layers 29, 39. The glue layer is preferably a medicaladhesive sold under the trade name Dymax. It may be UV curable for easeof manufacturing. This is also a suitable material for the glue layer 11of the system 1 of FIGS. 1 and 2.

The stent bed 5 shown in FIG. 3 is again of the tapering profile form.The tapered profile of the stent bed 5 has been discussed above withrespect to FIGS. 1, 2, 6 and 7. A non-tapered stent bed alternative wasalso discussed as well as a means for holding the stent device 4relative to the inner catheter that is positioned proximal of the stentdevice 4. Such alternative stent device holding means is also applicableto the system 30 shown in FIG. 3.

FIG. 3 also shows a guide sheath 41 of the stent device delivery system30 from which the inner catheter 3, the stent device 4 and the outersheath 22 extend to allow the stent device 4 to expand to the deploymentposition when the outer sheath 22 is retracted. The outer guide sheath41 can be made of conventional material that is suitably flexible tonavigate the vasculature of the patient yet suitably strong underendwise compression to allow it to be delivered to the target site by anoperative at a proximal end outside of the patient. Also shown in FIG. 3is the inner catheter 3 being made up of a conventional tube at a distalportion and a proximal guide portion 8 made of a slitted tubularmaterial and an outer tubular sleeve as described above with respect toFIGS. 1 and 2.

Deployment of the stent device delivery system 30 of FIG. 3 is effectedby subjecting the pull member 27 to a proximal pulling force. The pullmember 27 is securely attached to the outer layer 39 of the outer sheath36 by a combination of being captured between the laminated layers 29and 39 and also by adhesive attachment with these layers by the gluelayer 31. Thus, the outer layer 39 is moved proximally as the pullmember 27 is moved proximally and the outer layer 39 moves relative tothe inner layer 38 by action of the fold-over portion 40 rollingproximally. As the fold-over portion 40 moves proximally and begins touncover the stent device 4, the stent device 4 expands from the deliveryconfiguration shown in FIG. 3 to a deployed configuration. Once thefold-over portion 40 is proximal of the stent device 4, the stent device4 is able to fully deploy along the full axial length of the stentdevice 4. The fold-over portion 40 of the outer sheath 22 will continueto roll proximally as the pull member 27 is moved proximally until itreaches a connection portion 42 of the inner layer 38 of the outersheath 22 to the inner catheter 3. In the embodiment shown in FIG. 3,the connection portion 42 is releasable under a slight additionalpulling force on the outer layer 39 of the outer sheath 22 so that theouter sheath 22 can be retracted independently of the inner catheter, ifdesired.

The inner layer 38 of the outer sheath 22, in a portion overlaying thestent device 4, will be induced to share the tapering profile of thestent bed 5. Thus, a distal end of the inner layer 38 will have a largeroutside diameter than a proximal end of the inner layer 38. As thedistal end of the inner layer 38 folds over itself to form the rollingfold-over portion 40, at each instant the outer layer 39 has a largerdiameter in the vicinity of the rolling edge than the inner layer 38.This provides a gap between the inner layer 38 and the outer layer 39allowing the outer layer 39 to slide over the inner layer 39 withreduced opportunity sticking or catching between the two layers 38, 39.This feature thus both reduces deployment force of the rolling outersheath 22 and improves reliability of successful retraction of the outersheath 22. As will be described below, with reference to methods ofmanufacture of the stent device delivery systems disclosed herein, theinner layer 38 of the outer sheath 22 is preferably formed to have atapering profile substantially the same as the stent bed 5 to ensure theformation of the gap described above. The inner layer 38 may be formedto have the tapered profile by cold-drawing the inner layer 38.

In an alternative stent device delivery system to that shown in FIG. 3,the reinforcement layer 29 could be extended further so that it coversnot just the proximal portion 35 of the outer sheath 22, but also thetransition section 34 where the outer sheath 22 tapers radially inwardlythe distal portion 36 overlaying the stent device 4 the radially reducedproximal portion 35. The transition section 34 of the outer sheath 22 isat increased risk to failure and thus reinforcement of this portion, bythe lamination of the reinforcement layer 29 thereto, may beparticularly useful. The reinforcement layer 29 in this alternativeconfiguration thus captures the pull member 25 in a proximal portion ofthe reinforcement layer 29 while the reinforcement 29 continues distallybeyond the distal end of the pull member 27 to further act in areinforcement capacity for the transition section 34 of the outer sheath22. The reinforcement layer 29 may further extend distally beyond thetransition section 34 to overlay the stent device 4 and be laminated tothe distal portion 36 of the outer layer 39. This provides reinforcementto the outer layer 39 to avoid necking of the outer layer 39 which wouldotherwise cause the outer layer 39 to contact and compress the innerlayer 38, thereby causing the rolling action of the outer sheath 28 tostick and potentially fail. An extended reinforcement layer 29 wouldprovide the necessary resistance to such potential failure in the outerlayer 39 of the outer sheath 22.

In another alternative to that shown in FIG. 3, a heat shrink resistantsupport tube could be placed radially within the outer layer 39 and thereinforcement layer 29. The outer layer 39 and the reinforcement layer29 could be heat shrunk onto the support tube to further secure theattachment of the pull member 27. This means of attachment of the pullmember 27 to the outer sheath 34 is described below with respect to thedelivery system 60 shown in FIGS. 4 and 5.

In yet another alternative, the pull member 27 may be extended furtherdistally to that shown in FIG. 3 so as to overlay the stent device 4.The reinforcement layer 2 a would also be extended distally so that thepull member would still be captured radially between the laminated outerlayer 39 and reinforcement layer 29. Having the pull member 27 extendsubstantially to a distal end of the outer sheath 34 or at least so asto overlay the stent device can be advantageous as discussed earlierwith reference to FIGS. 1 and 2. In particular, the pull member 27provides tension support to the outer sheath 34 throughout the length ofsheath to which it is laminated.

The stent device delivery system 50 shown in FIGS. 4 and 5 is thepresently most preferred delivery system. It combines the low retractionforce of a rolling outer sheath 52 with full reinforcement by areinforcement layer 59, more reliable retraction of the outer sheath 52by the provision of a stent bed 5 having a tapering profile and secureattachment of the pull member 57 to the outer sheath 52 by lamination ofthe reinforcement layer 59 to an outer layer 69 of the outer sheath 52and also by means of other advantageous features that have not yet beendescribed.

In this system, the stent device 4 is radially constrained by the outersheath 52 into engagement with the tapered stent bed 5. The outer sheath52 comprises an inner layer 68 having an inner surface contacting anouter surface of the stent device 4 and an outer layer 69 that areconnected at a distal end of the outer sheath 52 by a fold-over portion70. The outer layer 69 is axially movable in the proximal directionrelative to the inner layer 68, which causes the fold-over portion 70 tomove proximally as well, thereby retracting the outer sheath 52. Theinner layer 68 of the outer sheath 52 is connected to the inner catheter3 at a connecting portion 72 located proximally of the stent device 4.The outer layer 69 of the outer sheath 52 extends further proximallyfrom the connecting portion 72 to a distal portion of a pull member 57.The distal portion of the pull member 57 is sandwiched between the outerlayer 69 and a reinforcement layer 59 that is laminated to the outerlayer 69 to attach the pull member 57 to the outer sheath 52. In thesystem 50 shown in FIG. 4, the reinforcement layer 59, as opposed to thesystem 30 shown in FIG. 3, is positioned radially outside of the outerlayer 69.

The reinforcement layer 59 and the outer layer 69 are laminated togetherto capture the distal portion of the pull member 57 and this ispreferably done by spreading a glue layer 61 axially along the fulllength of the reinforcement layer 59 and circumferentially around thereinforcement layer 59. The distal portion of the pull member 57 is,therefore, embedded in the glue layer 61 and adhered to thereinforcement layer 59 and the outer layer 69. The reinforcement layerextends further along the stent device delivery system 50 than in thesystem 30 shown in FIG. 3. The reinforcement layer 59 in the system 50shown in FIG. 5 extends substantially to a distal end or fold-overportion 70 of the outer sheath 52. The reinforcement layer 59, the gluelayer 61 and the outer layer 69 can together be considered an outerlayer of the outer sheath 52. The inner layer 68 and this combined outerlayer then make up the outer sheath 52. Accordingly, we will refer tothe layer 69 as the second layer and the combination of the second layer69, the glue layer 61 and the reinforcement layer 59 as the outer layer75 of the outer sheath 52 in the following.

Attachment of the distal portion of the pull member 57 to the outersheath 52 is enhanced by heat shrinking the second layer 69 and thereinforcement layer 59 with the distal portion of the pull member 57captured radially between these layers 59, 69. The reinforcement layer59 and the second layer 69 are heat shrunk onto a heat shrink resistantsupport tube 73. The heat shrinking serves to securely radially capturethe distal portion of the pull member 57 and compress the outer layer 75of the outer sheath 52 onto the heat shrink resistant support tube 73 tosecure them together. Further, the heat shrinking step provides athorough spreading of the glue layer 61, when done before the glue layer61 is set, to strongly adhere the distal portion of the pull member 57to the second layer 69 and the reinforcement layer 59 of the outersheath 52. The heat shrink resistant support tube 73 is movable axiallyrelative to the inner catheter 3 to allow the outer sheath 52 to bemoved relative to the inner catheter 3 and the stent device 4 so as tocarry out the process of retracting the outer sheath 52 and deployingthe stent device 4.

The inner layer 68 of the outer sheath 52 is heat shrunk at theconnecting portion 72 onto a heat shrink resistant portion of the innercatheter 3 at a location proximal of the stent device 4. This provides aconnection of the inner layer 68 to the inner catheter 3 sufficientlystrong to prevent slippage of the inner layer 68 relative to the stentdevice 4, yet peelable under normal retraction forces for retracting theouter sheath 52 to allow the outer sheath 52 and the inner catheter 3 tobe removed independently of one another after the stent device 4 hasbeen deployed, if this is desirable.

FIG. 5 shows a cross section of the stent device delivery systemallowing the circumferential extent of the distal portion of the pullmember 57 to be viewed. As can be seen, the pull member 57 comprises aproximal pull wire that has been flattened at the distal portion toprovide a low profile portion for fitting between the second layer 69and the reinforcement layer 75.

In the stent device delivery system 50 of FIGS. 4 and 5, the outer guidesheath 71 and the guide portion 8 of the inner catheter 3 are both madeof a slitted tubing for resisting endwise compressive stress and alsoallowing flexibility for navigating to the target stent site with anouter tubular sleeve layer overlaying the slitted tube.

In each of the delivery systems 1, 30, 50 of the Figs., the inner layeralong a portion overlaying the stent device 4 is preferably a cold-drawnpolymeric material. One reason for this is that the cold-drawn materialis relatively strong as compared to the pre-drawn material. Anotherreason is that the cold-drawn polymeric material has been found to beconducive to smooth and stick-free rolling in a rolling outer sheathconstruction. This is discussed in greater detail in WO 2010/076057 andWO 2010/076052, each of which are incorporated by reference in itsentirety into this application. There are manufacturing benefits to theuse of cold-drawn polymeric material for the outer sheath along aportion overlaying the stent device 4, as will be described below. Thus,preferably the inner layer 68, the second layer 69 and the reinforcementlayer 59 are cold-drawn along an axial portion of the outer sheath 52overlaying the stent device 4. In other words, the distal portion 66 ofthe outer sheath 52 is made of a cold-drawn polymeric material. Thepreferred cold-drawn material is polyethylene terephthalate (PET), butother polymeric materials capable of being both cold-drawn andheat-shrunk are useful.

The proximal portion of the outer sheath 52 is heat shrunk onto the heatshrink resistant support tube 73, which thus forms a reduced diameterportion of the outer sheath 52. A transition section 64, therefore,exists between the proximal portion 65 and the distal portion 66 of theouter sheath. The heat-shrunk proximal portion 65 of the outer sheath 52has been strengthened by this heat treatment, which again contributes toa reduced risk of breakage of the outer sheath at the proximal portion65. An example heat shrink resistant material for the support tube 73 ispolyimide.

In an alternative to that shown in the stent device delivery system 50of FIGS. 4 and 5, it can be envisaged that the reinforcement layer 59could be done away with. The distal portion of the pull member 57 couldbe captured radially between the support tube 73 and the outer layer 69by heat shrinking the outer layer 69 onto the support tube 73. Anadhesive layer could still be used to attach the distal portion of thepull member 57 to the outer layer 69 and the support tube 73. Theadhesive layer could also be used to attach the outer layer 69 to thesupport tube 73. A reinforcement layer could be applied in thisalternative construction, but extending just along a portion of theouter layer 69 overlaying the stent device 4 and perhaps also thetransition section 54 of the outer sheath 52. In another alternativeconstruction to the stent device delivery system 50 shown in FIGS. 4 and5, the reinforcement layer 59 may be laminated on the outer layer 69 ofthe outer sheath 52 along the proximal portion 65 of the outer sheathand not distally further. In another alternative, the reinforcementlayer 59 may be laminated to the outer layer 69 along the proximal, heatshrunk portion 65 and the transition section 64, but which does notoverlay the stent device 4.

The stent bed 5 in the system 50 is again formed into a taperingprofile, which tapers radially inwardly from a distal end to a proximalend. The inner layer 68 is formed to share substantially the sametapering profile so that it has a larger outside diameter at the distalend and a smaller outside diameter at the proximal end and taperssubstantially linearly therebetween. The second layer 69 is formed tohave a reverse taper, whereby the distal end adjacent the fold-overportion 70 has a smaller diameter than a proximal end at the proximalend of the stent device. The inner and outer layer 68, 69 are formedwith this taper in the manner described below, which involvescold-drawing a tube of material along a mandrel having a continuouslyincreasing outside diameter and then folding the tubing material backonto itself to provide two layers of material tapering in reversedirections. This feature of the inner layer 68 and the second layer 69,so as to have a taper in reverse directions, exaggerates a radial gapbetween the two layers during retraction of the outer sheath 52 to avoidthe possibility of the layers 68, 69 catching on one another. Catchingof the layers can create increased deployment force, and thus decreasedthe reliability of successful retraction of the outer sheath 52 from thestent device 4.

In the stent device delivery system 50 of FIGS. 4 and 5, the outersheath 52 is retracted from the stent device 4 by a rolling mechanism asdescribed with respect to FIG. 4. The pulling member 57 is subjected toa proximal pulling force, which will be transferred to the outer sheath52 because the distal portion of the pull member 57 is securely capturedradially between the support tube 73 and the second layer 69 on one sideof the pull member 57 and the reinforcement layer 59 on the other side.Further, the glue layer 61 bolsters the securement of the distal portionof the pull member 57 to the reinforcement layer 59 and the second layer69. The support tube 73 moves axially with the outer sheath 52 becausethe outer layer 75 of the outer sheath 52 is heat-shrunk onto thesupport tube 73. As the outer layer 75 moves proximally, the rollingfold-over portion consumes the inner layer 68 and extends the length ofthe outer layer 75 so as to progressively uncover the stent device 4 andallow the stent device 4 to expand to a deployed configuration. Once thefold-over portion 70 reaches the connection portion 72, where the innerlayer 68 is connected to the inner catheter, further pulling the pullmember 57 causes the connection portion 72 to peel away from the innercatheter 3 to disconnect the outer sheath 52 and the inner catheter 3.

In an alternative to the stent device delivery system 50 shown in FIGS.4 and 5, the pull member 57 could extend further distally so as to atleast partly overlay the stent device 4. The pull member 57 would stillbe laminated radially between the second layer 69 and the reinforcementlayer 61. The same proximal portion 65 of the outer sheath 52 would beheat shrunk onto the support tube 73. This would mean that an axialportion of the pull member 57 proximal of a very distal portion would becaptured by the heat shrunk portion of the outer sheath 52. In thispossible modification to the system 50 shown in FIGS. 4 and 5, a greateraxial portion of the pull member would have to be flattened to keep alow profile. The benefits of extending the pull member further towards adistal end of the outer sheath 52 has been discussed above with respectto FIGS. 1 and 2.

The reinforcement layer 59 is provided with a hydrophilic outer layer.This allows low friction delivery of the system 50 to the target tissuesite because the outer surface becomes extremely lubricous when it iscoated with water, as it would be in the vasculature of a patient.Providing the outermost surface of the outer sheath with a hydrophiliccoating is also applicable to the other delivery systems 10, 30 shown inFIGS. 1 to 3 and described above.

A method of manufacture of the stent device delivery systems of FIGS. 4and 5 is given in the following. The method steps required to providethe stent device delivery system 1 of FIGS. 1 and 2 and the stentdelivery device 30 of FIG. 3 will also be subsequently disclosed.

The stent device 4 must first be loaded into a tube of material, whichwill ultimately form at least part of the outer sheath 52. The stentdevice 4 is crimped into a reduced diameter configuration using a knowncrimping machine and transferred into the tube of outer sheath material.The inner catheter 3 having the stent bed 5 mounted thereon is thenplaced within the lumen of the stent device by simple insertion. Inorder to engage the stent device with the stent bed 5, the stent devicemust be further reduced in its radial dimension. To do so, the tube ofouter sheath material is cold-drawn along an axial portion where thestent device 4 is located. Necking of the tube of outer sheath materialduring this process reduces the diameter of the stent device and engagesthe outer surface of the stent bed 5 with the inner surface of the stentdevice 4. The cold-drawing process can be performed by hand and is bestdone by starting from a middle portion of the stent device 4 and pullingone way along the axis of the tube of outer sheath material with onehand and the other way with the other hand until the outside diameter ofthe stent device 4 can be reduced no more, which signifies strongengagement between the stent bed 5 and the stent device 4. This processis continued along the full length of the stent device 4 to put thestent device 4 into the radially reduced, delivery configuration shownin FIG. 4. This cold-drawing process is described in WO 2009/135934,which is incorporated by reference in its entirety into thisapplication.

A mandrel is then abutted against an end of the stent device 4, beingthe end that will become the distal end of the stent device. When astent bed 5 is used having a tapering profile, the distal end can beidentified by the end of the stent device 4 overlaying the largeroutside diameter end of the stent bed 5. The mandrel is placed withinthe tubular sheath and continues the profile of the outside diameter ofthe stent device 4 to give a surface against which an extension portionof the tube of outer sheath material can be cold-drawn. Preferably, themandrel tapers radially outwardly along its axis from an end in abutmentwith the stent device 4. The tapering profile of the mandrel hassubstantially the same gradient as the taper of the stent bed 5. Themandrel begins at the end abutted with the stent device 4 havingsubstantially the same outside diameter as the end of the stent device4. An extension portion of the tube of outer sheath material is formedby cold-drawing the tube against the mandrel for an axial length of atleast the length of the stent device and preferably slightly more toallow for manufacturing tolerance.

A distal end of the tube of outer sheath material has a small cut madein it, where distal is to be understood as in the direction from thestent device 4 to the extension portion. The cut allows the tube ofouter sheath material to be folded back upon itself so that theextension portion is reversed back to overlay the portion of the tube ofouter sheath material overlaying the stent device 4. A lubricantmaterial may be applied along the tube of outer sheath material beforeit is folded back onto itself in order to allow the portion that hasbeen folded back onto itself to move more freely relative to the innerlayer of material in contact with the stent device 4. These steps haveprovided a stent device 4 in a radially reduced delivery configurationengaging a stent bed 5. The stent device is held in the deliveryconfiguration by an inner layer 68 of cold-drawn polymeric materialengaging an outer surface of the stent device. An outer layer 69 thathas been folded back to provide the fold-over portion 70 overlaps theinner layer 68 in the axial direction. The outer layer 69 and the innerlayer 68 are tapered in reverse senses by this cold-drawing and foldingoperation.

In order to make the system 1 shown in FIGS. 1 and 2, a layer ofadhesive is applied along the tube of outer sheath material at leastalong a portion overlaying the stent device 4 and up to where thefold-over portion 12 will be once the folding operation has been carriedout. A pull member 7 is placed on the tube of outer sheath material sothat it overlays the stent device 4 and extends marginally beyond thestent device 4. The tube of outer sheath material is then folded backonto itself so as to form an outer layer 10 and an inner layer 9 and afold-over portion 12 connecting them. The outer layer 10 is movedrelative to the inner layer 9 until the fold-over portion 12 makescontact with the end of the pull member 7. The outer layer 10 can berotated back and forth relative to the inner layer 9 to spread the gluelayer 11 that is radially between them. The glue layer 11 is thenallowed to set or preferably is actively cured by application of UVradiation. In such a preferable case, the adhesive used is a UV curableadhesive, for example that sold under the trade name Dymax. An outersheath 2 as shown in FIGS. 1 and 2 is thus formed having an inner layer9, a fold-over portion 12 and an outer layer 10 that are formed into asingle laminar structure and having a pull member 7 positioned radiallybetween the two layers and embedded in the glue layer 11 adhering theinner and outer layers 9, 10 together.

Now described are the further steps necessary to form the stent devicedelivery system 30 shown in FIG. 3, starting from the stage of themanufacturing process for the system 50 of FIGS. 4 and 5 reached in theabove description. A further tube of sheath material is inserted intothe outer layer proximal of the stent device, which is into the endopposite where the fold-over portion 40 is located. The further tube ofouter sheath material forms the reinforcement layer 29. The outer layer39 and the reinforcement layer 29 are overlapped in the axial directionby a distance of about 5 cm. Before the tube of reinforcement layermaterial is inserted into the proximal portion of the outer layer 39, aglue layer 31 is applied to the end portion of the tube of reinforcementmaterial that will overlap in the axial direction with the proximalportion of the outer layer 39. The tube of reinforcement material isrotated circumferentially so as to spread the glue layer 31 uniformlyaround the circumference of the outer layer 31.

The remainder of the tube of reinforcement material that is notlaminated with the outer layer 39 is cut away. The distal portion of thepull member 37 is inserted into the glue layer 31 until it reaches thedistal end of the reinforcement layer 29. The distal portion of the pullmember is thus embedded in the glue layer and captured between thereinforcement layer 29 and the outer layer 39. In the preferredembodiment where the glue layer 31 is UV curable, the glue layer 31 isexposed to a UV light source so as to uniformly cure the adhesive. Thisis a simple to manufacture yet highly effective method of securing thepull member 27 to the outer sheath 34.

Referring back to the manufacture of the stent device delivery system 50shown in FIGS. 4 and 5, the tip member 6 has a bore in a proximal end tofit over the inner catheter 3. The tip member 6 is fitted to the innercatheter 3 in this manner. Holes extending radially through the tipmember 6 communicate with the inner catheter 3. A “dot” of glue isinjected into each of these holes to secure the tip member 6 to theinner catheter 3.

The heat resistant support tube 73 is inserted in a proximal end of theouter layer 69 radially inside the outer layer. The support tube 73 isinserted to axially overlap with the outer tube 69 for a length thatwill form the heat shrunk portion described above. The overlappingproximal portion of the outer layer 69 is then heat shrunk onto thesupport tube 73. The heat shrunk portion of the outer layer 69 will beabout 5 to 10 cm long.

Glue is applied to an outer surface of the outer layer 69 along an axialportion overlaying the stent device 4. A tube of reinforcement layermaterial is slid over the outer layer 69, substantially up to a proximalend of the outer layer 69, where a distal to proximal direction is inthe direction of the stent device 4 to the support tube 73 along theaxis of the system 50. Axially sliding the tube of reinforcement layermaterial in this way will spread the glue axially to the proximal end ofthe outer layer 69. The tube of reinforcement layer material 59 also isrotated to spread the glue uniformly in the circumferential direction.

The tube of reinforcement layer material is then cold-drawn along anaxial portion of the system 50 from a proximal end of the stent device 4to distal end of the outer layer 69. This serves to compact the distalportion 66 of the system 50 to ensure a reduced profile. Any excessmaterial of the tube of reinforcement layer extending beyond thefold-over portion 70 is cut away. The cold-drawing process alsouniformly squeezes the glue by spreading it axially along andcircumferentially around the reinforcement layer 59. Any excess glue canbe expelled from the distal end of the reinforcement layer 59. Thisallows a thin layer of glue to remain between the outer layer 69 and thereinforcement layer 59.

The axial portion of the reinforcement layer 59 overlaying the supporttube 73 is heat shrunk onto the support tube 73. This and the abovementioned heat shrinking process can be carried out using a thin heatblade at a temperature of 220° C. when a PET reinforcement layer 59 isbeing used. The heat blade ensures an accurate application of heat whereheat shrinking is to be carried out. In particular, the stent device 4is, because it is made of a temperature based memory material,particularly sensitive to being subjected to such a high temperature.Further, heat shrinking distally of the heat shrink resistant supporttube 73 would cause radial contraction in that area, which might blockor hinder the process of retraction of the outer sheath 52. Accordingly,it is only the portion of the reinforcement layer 59 and the outer layer69 overlaying the heat shrink resistant support tube that is subjectedto the high temperatures from the heat blade. Before the heat shrinkprocess is carried out, a distal portion of the pull member 57 isinserted into the glue layer 61 and radially between the reinforcementlayer 59 and the outer layer 69 so that the reinforcement layer 59, theouter layer 69 and the distal portion of the pull member 57 overlap inthe axial direction for a distance of about 5 cm. The heat shrinkingprocess serves to uniformly distribute the glue layer 61 around andalong the reinforcement layer 59 and also causes a thorough embedding ofthe distal portion of the pull member 57 in the glue layer 61.

The stent device delivery system 50 is subjected to ultraviolet lightalong where the glue layer 61 is present to cure the glue layer 61 andthus complete the lamination of the outer layer 69 and the reinforcementlayer 59.

Once the glue is set, the pull member 57 can be attached at a proximalend to a tension meter to determine the working force for retracting theouter sheath 52. Tests have been conducted and a maximum deploymentforce of below 20 N is consistently and reliably achieved with the stentdevice delivery system 50. An upper limit for the deployment force of 20N has been chosen to provide sufficient tolerance to guard against anypossibility of failure of the polymeric material used to create theouter sheath 52 from failing. Retraction of the outer sheath 52 is solow that that extremely thin (about 20 μm) polymeric layers of materialcan be safely used to construct a low profile stent device deliverysystem. Further, tests on the attachment of pull member to the outersheath 52 show that the pull member can be subjected to far greaterforces than that required to retract the outer sheath 52 before itseparates from the outer sheath 52.

What is claimed is:
 1. A stent device delivery system, comprising: astent device; an outer sheath comprising a first polymer-based layer, apolymer-based reinforcement layer, and a glue layer disposed between thefirst layer and the reinforcement layer wherein the outer sheathoverlays the stent device in a radially compact, delivery configurationof the stent device, the outer sheath retractable from a distal end ofthe stent device to a proximal end of the stent device to allow forradial expansion of the stent device to a deployed configuration; anouter catheter extending distally from a proximal end of the system andending proximally of the stent device wherein the outer catheter isdisposed radially outward of a proximal end of the outer sheath; aninner catheter extending axially and radially within a lumen of thestent device and providing a stent bed upon which the stent device islocated so that a radially inner surface of the stent device engages aradially outer surface of the stent bed, wherein the stent bed definesan inwardly tapering profile, narrowing in radius from a distal portionof the stent device to a proximal portion of the stent device; and apull member for retracting the outer sheath from the stent device,wherein the pull member is embedded in the glue layer, sandwichedbetween the first layer and reinforcement layer, and a proximal end ofthe pull member is disposed radially inward of the outer catheterwherein the outer sheath comprises an inner layer contacting an outersurface of the stent device, an outer layer and a fold-over portionconnecting the inner layer and the outer layer, so that proximalmovement of the outer layer relative to the inner layer causes thefold-over portion to move proximally axially relative to the stentdevice in a rolling manner and thus enables retraction of the outersheath.
 2. The stent device delivery system of claim 1, wherein thestent bed tapers such that a change in outer diameter of the stent beddivided by axial length over which the change in outside diameter occursis in the range of 0.0003 to 0.005.
 3. The stent device delivery systemof claim 2, wherein the stent bed tapers, such that a change in outerdiameter of the stent bed divided by axial length over which the changein outside diameter occurs is in the range of 0.0006 to 0.0009.
 4. Thestent device delivery system of claim 1, wherein the inwardly taperingprofile is stepwise.
 5. The stent device delivery system of claim 1,wherein the stent bed is axially continuous with respect to the stentdevice.
 6. The stent device delivery system of claim 1, wherein thestent bed is formed by a plurality of axially separated portions, eachof the plurality of axially separated portions having a constant outerdiameter less than an outer diameter of a distally positioned portion.7. The stent device delivery system of claim 1, wherein the stent bed ismade of a compressible material and the stent device is partiallyembedded in the stent bed in the radial direction.
 8. The stent devicedelivery system of claim 1, wherein the stent bed is made of a tackymaterial, which provides a radial as well as an axial holding force onthe stent device relative to the inner catheter such that duringexpansion of the stent device, the stent device peels away from thetacky material of the stent bed.
 9. The stent device delivery system ofclaim 1, wherein the stent bed is formed as a layer on the innercatheter.
 10. The stent device delivery system of claim 1, wherein theouter sheath is formed into a tapered profile with the inner layertapering radially inwardly from the distal portion to the proximalportion of the stent device and the outer layer progressively taperingradially outwardly along an entire length from the distal portion to theproximal portion of the stent device.
 11. The stent device deliverysystem of claim 1, wherein a portion of the outer sheath overlaying thestent device is formed having a tapering profile substantially followingthe tapering profile of the stent bed.
 12. The stent device deliverysystem of claim 1, wherein the outer sheath is made of a cold drawnpolymeric material at least along a portion thereof overlaying the stentdevice.
 13. The stent device delivery system of claim 1, wherein thefirst polymer-based layer comprises a polyethylene terephthalate. 14.The stent device delivery system of claim 1, wherein the polymer-basedreinforcement layer comprises a polyethylene terephthalate.
 15. Thestent device delivery system of claim 1, wherein the first polymer-basedlayer and the polymer-based reinforcement layer are directly attachedand in contact with the glue layer.